不同氮添加对轻木人工林生长及叶养分吸收的影响

Effects of different nitrogen additions on growth and leaf nutrient uptake of Ochroma lagopus plantation

关键词:  轻木, 氮添加, 叶绿素, 可溶性糖, 淀粉, 相关性

Key words:  Ochroma lagopus, nitrogen addition, chlorophyll, soluble sugar, starch, correlation

摘要:

为探究不同氮添加对轻木(Ochroma lagopus)人工林生长和叶养分吸收的影响。该文以1.5年生轻木为试验材料,设置0(N0)、50 kg·hm^-2尿素(N1)、100 kg·hm^-2尿素(N2)、50 kg·hm^-2缓释氮肥(PCU1)、100 kg·hm^-2缓释氮肥(PCU2)5个处理; 测定树高、胸径(DBH)及叶碳(C)、氮(N)、磷(P)、叶绿素和非结构性碳水化合物(NSC)含量。结果表明:(1)与N0处理相比,树高、DBH及叶绿素a、叶绿素b和叶绿素(a+b)含量在N2施肥处理下分别显著提高了28.66%、50.72%、50.17%、50.71%和50.25%(P<0.05)。(2)与N0处理相比,叶N含量在N2施肥处理下显著升高了60.16%(P<0.05); P含量呈下降趋势。N0处理下,叶N/P<14,轻木生长受N元素的限制,氮添加后N/P>14,添加氮肥改变了轻木生长受N元素的限制。(3)与N0处理相比,叶可溶性糖和NSC的含量在N2施肥处理下分别显著提高了78.98%和52.49%(P<0.05)。(4)尿素添加下叶的可溶性糖含量与N含量、C/P和N/P呈显著正相关,与P含量呈显著负相关; 缓释肥添加下叶淀粉含量与P含量呈显著负相关,与N/P呈显著正相关; 氮添加下叶可溶性糖和淀粉的含量与N含量、N/P呈显著正相关。(5)叶N、N/P、C/P、可溶性糖含量及可溶性糖/淀粉的表型可塑性指数均较大。主成分1(PC1)和主成分2(PC2)的累计方差贡献率为 66.3%。综上所述,氮添加对轻木生长及叶养分吸收有显著的促进作用,其中以N2施肥处理效果最优; 氮添加减缓了N元素对轻木生长的限制; 轻木通过增加叶绿素含量,提高叶片对N和P的利用效率,从而改变叶可溶性糖和淀粉含量的分布来促进轻木的生长。

Abstract:

To investigate the effects of different nitrogen applications on the growth and leaf nutrient uptake of Ochroma lagopus plantations, one- and a-half-year-old O. lagopus trees were used as experimental materials. Five treatments set up: 0(N0), 50 kg·hm^-2 urea(N1), 100 kg·hm^-2 urea(N2), 50 kg·hm^-2 slow-release nitrogen fertilizer(PCU1), and 100 kg·hm^-2 slow-release nitrogen fertilizer(PCU2); tree height, diameter at breast height(DBH), and leaf carbon(C), nitrogen(N), phosphorus(P), chlorophyll, and non-structural carbohydrates(NSC)contents were measured. The results were as follows:(1)Compared with the N0 treatment, tree height, DBH, chlorophyll a, chlorophyll b, and chlorophyll(a+b)contents were significantly increased by 28.66%, 50.72%, 50.17%, 50.71%, and 50.25%, respectively, under the N2 fertilization treatment(P<0.05).(2)Compared with the N0 treatment, leaf N content significantly increased by 60.16%(P<0.05)under the N2 fertilization treatment; P content showed a decreasing trend. Under the N0 treatment, leaf N/P<14, indicating that O. lagopus growth was limited by N element. After nitrogen addition, N/P>14, indicating that nitrogen fertilization altered the N-element limitation on O. lagopus growth.(3)Compared with the N0 treatment, leaf soluble sugar and NSC contents were significantly increased by 78.98% and 52.49%, respectively, under the N2 fertilization treatment(P<0.05).(4)Under urea application, the leaf soluble sugar content showed significant positive correlations with N content, C/P, and N/P, and a significant negative correlation with P content; under slow-release fertilizer application, the leaf starch content showed a significant negative correlation with P content and a significant positive correlation with N/P; under nitrogen application, the leaf soluble sugar and starch contents showed significant positive correlations with N content and N/P.(5)The phenotypic plasticity indices for leaf N, N/P, C/P, soluble sugar content, and soluble sugar/starch were all relatively high. The cumulative variance contribution rates of principal component 1(PC1)and principal component 2(PC2)were 66.3%. In summary, nitrogen addition significantly promotes the growth of O. lagopus and leaf nutrient absorption, with the N2 fertilization treatment yielding the best results; nitrogen addition alleviates the limiting effect of nitrogen on O. lagopus growth; O. lagopus promotes growth by increasing chlorophyll content, improving leaf utilization efficiency of nitrogen and phosphorus, and thereby altering the distribution of leaf soluble sugar and starch contents.